Hydrogen peroxide is a highly important commercial product widely used as a whitening agent in the textile or paper industries, as a disinfectant and as a basic product of the chemical industry, e.g. in the production of peroxide compounds (sodium perborate, sodium percarbonate, metallic peroxides or percarboxylic acids) in oxidation reactions (manufacture of amine oxides), epoxidation and hydroxylation (manufacture of plasticizers and stabilizers). It is further used for cleaning surfaces in the semiconductor industry, chemical polishing of copper, tin and other copper alloy surfaces, etching electronic circuits, etc.
The industrial method currently most widely used for the production of hydrogen peroxide is the autoxidation of alkylanthrahydroquinones. This process, which is comprised of a series of phases of reduction, oxidation, extraction, purification and concentration, is very complicated which makes the investments and variable costs very high. A very attractive alternative to this process is the production of hydrogen peroxide directly from the reaction between hydrogen and oxygen in the presence of metal catalysts of the platinum group, using explosive hydrogen concentrations (U.S. Pat. Nos. 4,681,751, 4,772,458, 4,832,938, 5,338,531), outside the explosivity limit (WO 99/41190, WO 01/05498, WO 01/05501, U.S. Pat. No. 6,168,775 B1). However, a high concentration of H+ and Br− ions is necessary in this process in the reaction medium to obtain high concentrations of hydrogen peroxide. Those ions are obtained from strong acids, such as sulphuric, phosphoric, hydrochloric or nitric and inorganic bromides. Nevertheless, working with high acid concentration solutions requires the use of special equipment to avoid corrosion. Furthermore, the presence of acid solutions and halogenated ions favours the solution of active metals (platinum group) which causes, firstly, the deactivation of the catalyst and, due to the very low dissolved metals concentration, its recovery is non-viable.
To avoid these inconveniences alternative processes have been proposed without the presence of halogen ions and/or acids in the reaction medium. For example, in the European patent no. EP 492064, a palladium based catalyst supported on a resin functionalized with halogens is proposed. The reaction medium is water with a hydrogen peroxide stabilising agent, but the H2O2 concentrations reached were only around 0.58% in weight. Another alternative (EP 504741), is the use of palladium catalysts supported on superacid inorganic solids, such as molybdenum, zirconium or wolfram, however, the hydrogen peroxide concentration reached did not exceed 1% in weight. In the European patent EP 978316, a process to obtain hydrogen peroxide solutions using palladium catalysts supported on active carbon functionalized with sulphonic groups is described. Nevertheless, said method requires many stages, it is very complicated to control the quality of the initial active carbons and the catalysts are difficult to reproduce.
Thus, there is the necessity to have new catalysts available which permit obtaining hydrogen peroxide by means of a direct reaction with hydrogen and oxygen in the presence of said catalysts, easily preparable and reproducible, and of a solvent, to obtain high concentration non-corrosive hydrogen peroxide solutions with high selectivity.